Feed mechanism and presser foot arrangement

ABSTRACT

A multiple needle felling machine including a main feed bar and a differential feed bar connected, respectively, to a main feed dog and a differential feed dog each having several rows of teeth with one row being higher than the other rows and the teeth on the respective feed dogs facing in opposite directions. A multiple-section presser foot cooperates with the feed dogs and includes a spring-loaded yielding section to clamp the thread chain to insure nonskipping at the start of sewing operations.

United States Patent Robert A. Hayes Franklin Park; v

James A. Frendreis, Chicago, both of III. 857,929

Sept. 15, 1969 Oct. 19, 1971 Union Special Machine Company Chicago, Ill.

Inventors Appl. No. Filed Patented Assignee FEED MECHANISM AND PRESSERFOOT ARRANGEMENT 17 Claims, 14 Drawing Figs.

US. Cl 112/235, 1 12/216 Int; Cl ..D05b 27/02, D05b 29/00 Field ofSearch l 12/235-240, 216, 215

{56] References Cited UNITED STATES PATENTS 2,370,738 3/1945 Kucera ll2/235 2,627,240 2/1953 Johnson et al. 112/235 2,671,422 3/1954,Tamburro et al. l 12/2'35 Primary Examiner- Patrick D. LawsonAn0rney-Diller, Brown, Ramik & Holt ABSTRACT: A multiple needle fellingmachine including a main feed bar and a differential feed bar connected,respectively, to a main feed dog and a differential feed dog each havingseveral rows of teeth with one row being higher than the other rows andthe teeth on the respective feed dogs facing in opposite directions. Amultiple-section presser foot cooperates with the feed dogs and includesa spring-loaded yielding section to clamp the thread chain to insurenonskipping at the start of sewing operations.

PATENTEDUBT 19 I97! 3,613, 09

-- SHEET10F'3 lNVE/VTURS QOBEET A. HAYES JAMES A.FRENDRE|$ v ATTORNEYSWWW ml 3,613,609

SHEET 2 OF 3 /NVN TURS RUBEWT A. HAYES 6"- JAMES A. FRENDREIS ATTORNEYSkm uiffnum 1s l97| sum 3 0F 3 yawn INVENTUR5 ROBERT A. HAYES 6 JAMESA.FRENDREIS ATTORNEYS FEED MECHANISM AND PRESSER FOOT ARRANGEMENTCROSS-REFERENCES TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION 1.Field of the Invention The new feed mechanism and presser footarrangement herein disclosed is particularly adaptable for use on adifferential feed-off-the-arm machine and can also be employed on a flatbed machine with a differential feeding mechanism.

2. Description of the Prior Art Previously known types offeed-off-the-arm machines were designed for heavy weight materials suchas denim or overall material. Such machines are not completelysatisfactory for use with lightweight woven materials or lightweightknit materials.

The presser foot in some known types of machines includes a yieldingsection on the rear portion of the presser foot. Such known yieldingsections were only able to move up or down and such movements are notentirely satisfactory.

Various types of presser foot arrangements have been devised but whenthe presser foot was raised to insert the material, the whole foot wouldlift off of the throat plate. In doing this, the thread chain is notheld on the throat plate in a line directly behind the needle slots, butis free to lay in any direction from the needle slots. This results inskipping of the first few stitches on the material.

SUMMARY OF THE INVENTION The main object of the present invention is toprovide pucker-free felled seams.

The feed-off-the-arm machine herein'disclosed is of the same type asthat which has been previously disclosed in U.S. Pat. No.3,416,473.!Idwever, the present machineis particularly designed forlightweight woven materials and some lightweight knit materials such asthe type used for men's dress shirts.

A main feed dog and a differential feed dog are disclosed as having onerow of their teeth stepped up in relation to the other rows of teeth.The teeth on the main feed dog are facing in the normal manner in thedirection of the feeding stroke. The teeth on the differential feed dogare facing against the direction of the feeding stroke. When sewingwoven materials the differential feed dog is set for a shorter travelthan the main feed dog. The combination of the shorter travel and theoppositely facing teeth of the differential feed dog tends to hold backthe material while the greater stroke of the main feed dog willtherefore cause the material to be slightly stretched as it is beingsewed. The thread is also in a slightly stretched condition as thestitches are being formed. Upon leaving the feed dogs both the materialand the stitching will return to their normal conditions resulting in aflat pucker-free seam.

When sewing knit material, the differential feed dog is set for aslightly greater travel than the main feed dog. This will cause thematerial to be slightly gathered as it is being sewed. The reason forgathering when sewing knit material is that, as the operator ispresenting the material to the machine, the material has a tendency tostretch slightly. Therefore, the feed dogs will gather the materialpartly back to its original condition while it is being sewed. Hereagain, the thread is in a slightly stretched condition as the stitchesare formed. Therefore, upon leaving the feed dogs, the material willfully return to its normal condition along with the thread. Thus, theresult will be a flat pucker-free seam.

A further object of the present invention is to provide a presser footmade up of three sections, each having a stepped portion correspondingto the stepped row of teeth on the feed dogs. The stepped portions onboth the presser foot and feed dogs serve to produce a straight seamfree from any curvature.

Another object of the present invention is -.to construct a presser footso that more pressure is applied on the front section than on theremaining sections. For example, with the present invention, if 20pounds of pressure is applied to the presser bar the resulting pressureon the presser foot will be I 0 pounds on the front foot section andonly 5 pounds on therear foot section and middle foot section. Thisgreater pressure applied by the front section against the differentialfeed dog further serves to hold the material back while the main feeddog is stretching it.

A further object of the present invention is to provide an improvedpresser foot having a yielding section on the rear portion thereofwherein the yielding section is permitted to float, or pivot, on a pairof springs in the rear portion of the'presser foot.

A further object of the present invention is to provide an improvedpresser foot which aids the operator in beginning the stitching on thematerial. The improved presser footis constructed so that the operatoris able to lift the front foot section while the other foot sectionsremain in contact with the throat plate. In this way, the yieldingsection on the rear foot portion clamps the'thread chain flat againstthe throat plate in a line directly behind the needle slots. Therefore,no skipping will result during the first few stitches on the material.The operator can also lift the whole foot off of the work if she pleasesby applying more pressure to the foot treadle or other means.

Another object of the present invention is to provide a novel method andapparatus by which a main feed dog and a differential feed dog combinewith the novel presser foot to produce pucker-free seams.

A still further object of the present invention is to provide acombination of a plurality of feed dogs having teeth opposing each otherand having one row of teeth on each feed dog stepped up and in line witheach other.

With the above and other objects in view that will hereinafter appear,the nature of the invention will be more clearly understood by referenceto the following detailed description, the appended claimed subjectmatter andthe several views illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a fragmentary sideelevational view, partly in sec tion, of the sewing machine employingthe present invention.

FIG. 2 is a partial plan view of the work-supporting arm showing thearrangement of the feed dogs in the throat plate.

FIG. 3 is an elevational view of the presser foot as shown in FIG. 1.

FIG. 4 is a plan view of the presser foot shown in FIG. 3.

FIG. 5 is a plan view partly in section taken along line 5-5 of FIG. 3.

FIG. 6 is an elevational view partly in section along line 6- 6 of FIG.3.

FIG. 7 is a sectional view taken along line 7-7 of FIG. 3.

FIG. 8 is a sectional view taken along line 8-8 of FIG. 3.

FIG. 9 is a sectional view taken along line 9-9 of FIG. 3.

FIG. 10 is a detail view in elevation of the main feed dog.

FIG. 11 is a sectional view taken along line 11-11 of FIG. 10.

FIG. 12 is a detail view in elevation of the differential feed dog.

FIG. 13 is an end view of the differential feed dog of FIG. 12.

FIG. 14 is a fragmentary sectional view taken along line 14-14 of FIG.2, and including the workpiece material and a section of the presserfoot.

DESCRIPTION OF THE PREFERRED EMBODIMENT The sewing machine frame and thevarious driving mechanisms therein are the same as those disclosed inU.S. Pat. No. 3,416,473.

Within the work supporting arm extends a looper rock shaft 11 carryinglooper holders 12 at one of its ends. Loopers 13 are mounted in thelooper holders 12 within the work supporting arm 10. These loopers arelocated beneath the needles 14 which are carried by the needle bar 15.The needle bar, in turn, is slidably carried in the needle head 16.

Also within the arm' 10 extends a differential feed bar 17 which carriesa differential feed dog 18 at its front end. The feed dog 18 is securedby a screw 19 to the feed bar 17. The feeddog is adjustable up and downby means of the elongated slot 20. v

A main feed bar 21 is provided aridalso extends within the arm 10. Tothe front endofbar 21 is secured, by a screw 22, a main feed dog 23. Anelongated slot 24 in the main feed dog 23 allows the feed dog to beadjusted up or down. The feed bars 17 and 21, and their feed dogs 18 and23, are driven and adjusted in a manner as that which has beenpreviously described in U.S. Pat. No. 3,416,473.

The front end of the work supporting arm 10 supports a throat plate 25.The throat plate is provided with a raised or stepped up portion 26along one side. This step portion 26 has a feed slot 27 disposedlongitudinally therein. The main or lower surface 28 of the throat platehas a series of parallel feed slots 29. The feed slots 29 aresubstantially as long as the feed slot 27. The throat plate 25 also hastwo needle slots 30 located and spaced to correspond with the needle 14.

The feeding surface of the main feed dog 23 has several rows of teethwith one row of teeth 31 being slightly higher than the other rows ofteeth 32. The higher one row of teeth 31 registers in the rearwardportion of the feed slot 27 of the throat plate 25 with the other rowsof teeth 32 registering in therearward portion of the feed slots 29.

The feeding surface of the differential feed dog 18 has several rows ofteeth with the teeth facing opposite the direction of the main feed dogteeth 31 and 32. One row of teeth 33 is slightly higher than the otherrows of teeth 34. The higher row of teeth 33 registers in the forwardportion of the feed slot 27 with the other rows of teeth 34 registeringin the forward portion of the feed slots 29. i

A three section presser foot 35 is mounted above the throat plate 25 toa'presser bar 36. The three sections of the presser foot cooperate withthe feed dogs 18 and 23 to produce the flat pucker-free felled seam thatis desired.

' A presser foot shank 37 is secured to a presser bar 36 by a screw 38and has two downwardly and forwardly extending legs 39 and 40. Theselegs are pivotally secured, by screws 41, intermediate the ends of arms42 and 43 of a presser foot bracket 44. At the forward ends of arms 42and 43 there is pivotally secured, by first pivot screws 45, a frontpresser foot section 46. This front foot section 46 is located above andcooperates with the differential feed dog 18. The bottom of frontpresser foot section 46 is made up of two separate surfaces 47 and 48.Surface 47 cooperates with the lower rows of teeth 34 on thedifferential feed dog 18 while surface 48 is cut to a depth that willcorrespond to the higher row of teeth 33 on the differential feed dog18.

The rearward end of presser foot bracket 44 embraces a hinged section 49(FIG. 8) intermediate its ends and is pivotally secured thereto by apivot screw 50. At the forward end of the hinged section 49 there ispivotally secured, by a screw 51, a second or middle presser footsection 52. This presser foot section 52 is located immediately behindand in line with the front presser foot section 46. it also is above andin cooperation with the front portion of the main feed dog 23. The footsection 52 is provided with needle slots 53 located to coincide with theneedle slots 30 in the throat plate 25. The bottom of foot section 52 isalso made up of two separate surfaces 54 and 55 in order to correspondto the difference in height of the rows of teeth 32 and 31 on the mainfeed dog 23.

At the rearward end of hinged section 49 there is pivotally secured, byscrew 56, a rear presser foot section 57. This presser foot section 57is immediately behind and in line with the middle presser foot section52 and is located above the rear portion of the main feed dog 23 forcooperation therewith. The rear presser foot section 57 carries aspringloaded yielding section 58 confined in a slot 59 on the bottom ofthe foot section 57. A pair of springs 60 and 61 serve to force theyielding section 58 toward the work. Springs 60 and 61 are confined inbores in the bottomof the hinged section 49 and pass through holes inthe bottom of the rear presser foot section 57. The yielding section 58has upwardly and inwardly turned lips 62 at each end which serve to keepit attached to the foot section. On the bottom of the foot section 57there are first and second separate material engaging surfaces 63 and 64that correspond to the difference in height of the rows of teeth 32, Menthe main feed dog 23. Slot 59 is cut to a greater depth than surface 64so that as a seam is being sewed the yielding section 58 can be pushedup so that it will be in the same plane as the surface 64.: After apiece of material has been sewed, the yielding section 58 will be pusheddown to clamp the thread chain to insure against skipping at thebeginning of the next piece of material.

One end of a hold-down spring 65 is fitted into a bored hole 66 in theend of the presser bar 36. The other end of the spring 65 fits over athreaded pin 67 secured'in the top surface of the hinged section 49. Thepin 67 and the spring 65 are located on the center line of the presserbar 36. The spring 65 applies a downward pressure on the hinged section49 and, in turn, to the presser foot sections 52 and 57. Therefore, asthe presser bar 36 is raised slightly, the presser foot shank 37 willbegin to raise the presser foot bracket 44 pivoting on screws 41. As thepresser foot bracket 44 raises, it will pivot on the screw 50 and willalso raise the front presser foot section 46. Because of the pressure ofspring 65, the middle and rear. presser foot sections 52 and 57 will notbe lifted and therefore will enable the yielding sections 58 to clampthe thread chain to insure nonskipping of the first few stitches at thebeginning of the next piece of material.

The preferred form on the invention has been described and illustrated,it being understood that the purposes of the invention can also beaccomplished by minor changes in individual parts and arrangementswithin the'spirit and scope of the invention.

We claim: v l

1. In a sewing machine, a presser foot having a plurality of sectionsincluding a front foot section, a rear foot section, and a middle footsection, means for connecting the respective foot sections to a presserbar, said means including arm means having a forward end and a rearwardend, leg means pivotally connected to said arm means, first pivot meansconnecting said front foot section to said forward end of said armmeans, and second pivot means connecting said rear foot section and saidmiddle foot section to said rearward end of said arm means.

2. Apparatus as in claim 1 wherein said second pivot means includes ahinged section having a forward end and a rearward end, and meanspivotally connecting said middle foot section to the forward end of saidhinged section and said rear foot section to the rearward end of saidhinged section.

3. In a sewing machine, a presser foot having a plurality of sectionsincluding a front foot section and a rear foot section, a presser barconnected to said presser foot for applying pressure thereto,distributing means for distributing more of said pressure to said frontfoot section than to said rear foot section, said distributing meansincluding leg means extending downwardly from said presser foot, armmeans having a forward end and a rearward end, means pivotallyconnecting said arm means intermediate said forward end and rearward endto said leg means, first pivot means connecting said front foot sectionto the forward end of said arm means, a hinged section having a forwardend and a rearward end, second pivot means connecting said hingedsection to said rearward end of said arm means, a middle foot section,means connecting said middle foot section to the forward end of saidhinged section, and means connecting said rear foot section to therearward end of said hinged section.

4. In a sewing machine, a presser foot having a plurality of sectionsincluding a front foot section and a rear foot section, a presser barconnected to said presser foot for applying pressure thereto,distributing means for distributing more of said pressure to said frontfoot section than to said rear foot section, means for raising saidfront foot section following a sewing operation, and holddown means forprecluding upward movement of said rear foot section.

5. Apparatus as defined in claim 4 wherein said holddown means comprisesspring means operatively disposed intermediate said rear foot sectionand said presser bar.

6. In a sewing machine, a presser foot having a plurality of sectionsincluding a front foot section and a rear foot section, a presser barconnected to said presser foot for applying pressure thereto, andholddown means operatively disposed between said presser bar and saidrear foot section for precluding movement of said rear foot section whensaid presser bar is operated to raise said front foot section, said rearfoot section including a yielding section located in spaced relation onthe underside thereof, and biasing means urging said yielding sectiondownwardly from said rear foot section for engagement with a threadchain between sewing operatrons.

7. Apparatus as defined in claim 1 including a main feed dog havingmaterial-feeding teeth thereon facing in the direction of feed, and adifferential feed dog having material-feeding teeth thereon facingopposite the direction of the teeth on said main feed dog; said mainfeed dog being located for cooperating with said rear foot section, saiddifferential feed dog being located for cooperating with said front footsection.

8. In a sewing machine, a presser foot having a plurality of sectionsincluding a front foot section and a rear foot section, a presser barconnected to said presser foot for applying pressure thereto,distributing means for distributing more of said pressure to said frontfoot section than to said rear foot section, a main feed dog havingmaterial-feeding teeth thereon facing in the direction of feed, and adifferential feed dog hav-' ing material-feeding teeth thereon facingopposite the direction of the teeth on said main feed dog; said mainfeed dog being located for cooperating with said rear foot section, saiddifierential feed dog being located for cooperating with said front footsection.

9. In a sewing machine, a presser foot having a plurality of sectionsincluding a front foot section and arear foot section, a presser barconnected to said presser foot for applying pressure thereto, holddownmeans operatively disposed between said presser bar and said rear footsection for precluding movement of said rear foot section when saidpresser bar is operated to raise said front foot section, a main feeddog having material-feeding teeth thereon facing in the direction offeed, and a differential feed dog having material-feeding teeth thereonfacing opposite the direction of the teeth on said main feed dog; saidmain feed dog being located for cooperating with said rear foot section,said differential feed dog being located for cooperating with said frontfoot section.

10. In a sewing machine including a presser foot, said presser footcomprising first and second material-engaging surfaces separated by aslot extending upwardly therebetween, a yielding section confined insaid slot, spring means confined in said slot between said yieldingsection and said presser foot for urging said yielding section towardthe work, said spring means engaging said yielding section at a rearwardportion thereof for allowing a forward portion of said yielding sectionto be raised higher than said rearward portion.

11. Apparatus as defined in claim 10 wherein said yielding sectionincludes intumed lip means engaging a portion of said presser foot forretaining said yielding section with said slot means.

12. In a sewing machine, a main feed dog having a plurality of rows ofmaterial-feeding teeth thereon with all of the teeth facing in a firstdirection, and a differential feed dog having a plurality of rows ofmaterial-feeding teeth thereon with all of the teeth facing in a seconddirection from said first direction, at least one row of teeth on saidmain feed dog and at least one row of teeth on said differential feeddog being stepped up from the remaining rows of teeth.

13. Apparatus as defined in claim 12 wherein the stepped rows of teethon said main feed dog and said difi'erential feed dog are in line witheach other.

14. Apparatus as defined in claim 12 including a presser foot having aplurality of sections including a front foot section and a rear footsection, said main feed dog being located for cooperating with one ofsaid plurality of sections, and said differential feed dog being locatedfor cooperating with another one of said plurality of sections.

15. Apparatus as defined in claim 13 including a presser foot having aplurality of sections including a front foot section and a rear footsection, said main feed dog being located for cooperating with one ofsaid plurality of sections, and said differential feed dog being locatedfor cooperating with another one of said plurality of sections.

16. A method of producing a pucker-free seam when sewing woven materialscomprising the steps of providing a main feed dog with material-feedingteeth thereon facing in the direction of material feed, providing adifferential feed dog with material-feeding teeth thereon facing in thedirection opposite from the direction of material feeding, andcontrolling the length of travel of said diflerential feed dog so it isshorter than the length of travel of said main feed dog.

17. A method of producing a pucker-free seam when sewing knit materialscomprising the steps of providing a main feed dog with material feedingteeth thereon facing in the direction of material feed, providing adifferential feed dog with material-feeding teeth thereon facing in thedirection opposite from the direction of material feeding, andcontrolling the length of travel of said differential feed dog so it islonger than the length of travel of said main feed dog.

1. In a sewing machine, a presser foot having a plurality of sectionsincluding a front foot section, a rear foot section, and a middle footsection, means for connecting the respective foot sections to a presserbar, said means including arm means having a forward end and a rearwardend, leg means pivotally connected to said arm means, first pivot meansconnecting said front foot section to said forward end of said armmeans, and second pivot means connecting said rear foot section and saidmiddle foot section to said rearward end of said arm means.
 2. AppAratusas in claim 1 wherein said second pivot means includes a hinged sectionhaving a forward end and a rearward end, and means pivotally connectingsaid middle foot section to the forward end of said hinged section andsaid rear foot section to the rearward end of said hinged section.
 3. Ina sewing machine, a presser foot having a plurality of sectionsincluding a front foot section and a rear foot section, a presser barconnected to said presser foot for applying pressure thereto,distributing means for distributing more of said pressure to said frontfoot section than to said rear foot section, said distributing meansincluding leg means extending downwardly from said presser foot, armmeans having a forward end and a rearward end, means pivotallyconnecting said arm means intermediate said forward end and rearward endto said leg means, first pivot means connecting said front foot sectionto the forward end of said arm means, a hinged section having a forwardend and a rearward end, second pivot means connecting said hingedsection to said rearward end of said arm means, a middle foot section,means connecting said middle foot section to the forward end of saidhinged section, and means connecting said rear foot section to therearward end of said hinged section.
 4. In a sewing machine, a presserfoot having a plurality of sections including a front foot section and arear foot section, a presser bar connected to said presser foot forapplying pressure thereto, distributing means for distributing more ofsaid pressure to said front foot section than to said rear foot section,means for raising said front foot section following a sewing operation,and holddown means for precluding upward movement of said rear footsection.
 5. Apparatus as defined in claim 4 wherein said holddown meanscomprises spring means operatively disposed intermediate said rear footsection and said presser bar.
 6. In a sewing machine, a presser foothaving a plurality of sections including a front foot section and a rearfoot section, a presser bar connected to said presser foot for applyingpressure thereto, and holddown means operatively disposed between saidpresser bar and said rear foot section for precluding movement of saidrear foot section when said presser bar is operated to raise said frontfoot section, said rear foot section including a yielding sectionlocated in spaced relation on the underside thereof, and biasing meansurging said yielding section downwardly from said rear foot section forengagement with a thread chain between sewing operations.
 7. Apparatusas defined in claim 1 including a main feed dog having material-feedingteeth thereon facing in the direction of feed, and a differential feeddog having material-feeding teeth thereon facing opposite the directionof the teeth on said main feed dog; said main feed dog being located forcooperating with said rear foot section, said differential feed dogbeing located for cooperating with said front foot section.
 8. In asewing machine, a presser foot having a plurality of sections includinga front foot section and a rear foot section, a presser bar connected tosaid presser foot for applying pressure thereto, distributing means fordistributing more of said pressure to said front foot section than tosaid rear foot section, a main feed dog having material-feeding teeththereon facing in the direction of feed, and a differential feed doghaving material-feeding teeth thereon facing opposite the direction ofthe teeth on said main feed dog; said main feed dog being located forcooperating with said rear foot section, said differential feed dogbeing located for cooperating with said front foot section.
 9. In asewing machine, a presser foot having a plurality of sections includinga front foot section and a rear foot section, a presser bar connected tosaid presser foot for applying pressure thereto, holddown meansoperatively disposed between said presser bar and said rear foot sectionfor precluding moVement of said rear foot section when said presser baris operated to raise said front foot section, a main feed dog havingmaterial-feeding teeth thereon facing in the direction of feed, and adifferential feed dog having material-feeding teeth thereon facingopposite the direction of the teeth on said main feed dog; said mainfeed dog being located for cooperating with said rear foot section, saiddifferential feed dog being located for cooperating with said front footsection.
 10. In a sewing machine including a presser foot, said presserfoot comprising first and second material-engaging surfaces separated bya slot extending upwardly therebetween, a yielding section confined insaid slot, spring means confined in said slot between said yieldingsection and said presser foot for urging said yielding section towardthe work, said spring means engaging said yielding section at a rearwardportion thereof for allowing a forward portion of said yielding sectionto be raised higher than said rearward portion.
 11. Apparatus as definedin claim 10 wherein said yielding section includes inturned lip meansengaging a portion of said presser foot for retaining said yieldingsection with said slot means.
 12. In a sewing machine, a main feed doghaving a plurality of rows of material-feeding teeth thereon with all ofthe teeth facing in a first direction, and a differential feed doghaving a plurality of rows of material-feeding teeth thereon with all ofthe teeth facing in a second direction from said first direction, atleast one row of teeth on said main feed dog and at least one row ofteeth on said differential feed dog being stepped up from the remainingrows of teeth.
 13. Apparatus as defined in claim 12 wherein the steppedrows of teeth on said main feed dog and said differential feed dog arein line with each other.
 14. Apparatus as defined in claim 12 includinga presser foot having a plurality of sections including a front footsection and a rear foot section, said main feed dog being located forcooperating with one of said plurality of sections, and saiddifferential feed dog being located for cooperating with another one ofsaid plurality of sections.
 15. Apparatus as defined in claim 13including a presser foot having a plurality of sections including afront foot section and a rear foot section, said main feed dog beinglocated for cooperating with one of said plurality of sections, and saiddifferential feed dog being located for cooperating with another one ofsaid plurality of sections.
 16. A method of producing a pucker-free seamwhen sewing woven materials comprising the steps of providing a mainfeed dog with material-feeding teeth thereon facing in the direction ofmaterial feed, providing a differential feed dog with material-feedingteeth thereon facing in the direction opposite from the direction ofmaterial feeding, and controlling the length of travel of saiddifferential feed dog so it is shorter than the length of travel of saidmain feed dog.
 17. A method of producing a pucker-free seam when sewingknit materials comprising the steps of providing a main feed dog withmaterial feeding teeth thereon facing in the direction of material feed,providing a differential feed dog with material-feeding teeth thereonfacing in the direction opposite from the direction of material feeding,and controlling the length of travel of said differential feed dog so itis longer than the length of travel of said main feed dog.